Parts of a House Window

Glass windows have been around for hundreds of years, and their terminology and parts are much the same today as they were when they were first invented. Advances have been made in window materials and operation, but the basic parts remain unchanged.

Jamb

The window jamb is the frame that goes around the window and separates it from the wall. The jamb also contains the tracks that the windows slide up and down on.

Sash

The thick wooden frame that surround the glass on the perimeter of a window is called a sash. Most operable windows contain two sashes, one upper and one lower, that slide up and down in the jamb. Casement windows are hinged on one side and open by means of a hand-turned screw and consist of a single sash.

Muntins

Muntins are the slender pieces of wood that divide the individual glass panes in a window sash. In the past, muntins were common and allowed smaller, easier-to-produce and therefore less expensive pieces of glass to be knit together to form large windows. Today, most muntins are made of metal or are actually decorative as they are applied between the panes of double-pane windows that are made from large pieces of glass. Sometimes they are applied to the surface instead. Muntins used in this manner are usually referred to as grilles.

Lites

Also known as panes, these are the actual glass pieces of the window. Originally, all lites were single pane, meaning that one piece of glass was used in each lite. In the last 20 to 30 years, double-pane windows that trap gas between them as an insulator have become the norm. Today, many windows consist of two large panes, one on the inside and one on the outside of the window, that fill the sash and encase gas, commonly argon, between them.

Stool

The window stool, also called the window sill, is the horizontal piece of wood found at the bottom of a window jamb. The bottom sash usually closes against it, and the stool will many times extend past the edge of the jamb.

Trim

Technically, window trim is not part of the window. It is the decorative molding that hides the gap between the window jamb and the wall.

Locks

Windows are locked by one of two methods. A sash lock can be placed on the top of the bottom sash and activated by turning it so it fits into a mating piece on the bottom of the top sash. When the two are connected the window can't be moved up or down. Earlier locking mechanisms consisted of a small round bar that was inserted in holes drilled from through the top of the bottom sash into the bottom of the top sash. This accomplished the same thing as a sash lock, but less expensively and without the moving pieces.